Timing system



April 6, 1948, 1.. A. DE ROSA I 2,438,904

TIMING SYSTEM Filed Nov. 23, 1942 I 3 Sheets-Sheet l KECE/VER CLIPPERCIRCUIT h :62

CIRCUIT IN VEN TOR. L 00/5 v ,4. DE ROS/4 ATTORNEY Ap 1948- 1.. A. DElos v 2,438,904

TIMING SYSTEM I Filed Nov. 25, 1942 3 Sheets-Sheet 2 INVEN TOR. LOU/5fl. DEROSH ATTORNEY April 6, 1948. L. A. DE ROSA 2,438,904

TIMING SYSTEM Filed Nov. 23, 1942 3 Sheets-Sheet 3 7?- J 00 T PUT IN VENTOR. L OU/ fl. DE RUSH ATTOM Patented Apr. 6, 1948 UNITED OFFI -(ZE;

2,438,904. TIMING SYSTEM Louis A; de Rosa, Staten Island, .N. Yassignorto. Federal: Telephone. and Radio. Corporatiom. Newark, N. J a'.corporationofDelaware Application.Novemberi23, 1942,:SerialN'o'. 466,557

This. invention relatestoradiodetection: SYS-J tems and more.particularly to a..= method;and-.

means for calibratinglthe screennof the indicating oscillograph'oroscillographstof thegsystem.

Radio detection systemsitowhich this invention relates are of thecharacter: which transmits a; high voltagesimpulsa and then: detectsechoesthereof causedby the: presence. of. obstacles.- within therangeof. the systcm.-., By means *Of;

directive antenna. equipment Lands suitable itiming means, the azimuthand .elevation. of iand the distance to any..-particular. obstacle,causingxam echo can be determined" Such: systems are .tparsticularlyuseful in detecting andrdetermining; lo-

cations of enemy aircraft'and -ships. Systems of:

this character are disclosed in :copending applications of 'H.Busignies, Serial, No. 381,640, filed:

March 4, 1941, entitled: Position: finding system for gunfire controlandserial No; 458,191, fi-led;-i

September 14,- 1942, 2,423,304; entitled Pulse generatingasystem.

now: Patent i Number It has been proposed: heretofore to use thentransmitted impulses, especially where theirsioc currence is at anunsteady frequency; ,toshock excite an L-C circuit and to usetheiiresulting damped waves or pulse markers generated-there by tocalibrate the screen; of the oscill'ograplr;

However, marksproduced byza' dampedwave 3136:; not alwayssatisfactoryrbecause the amplitude ofr' the oscillations-of thewaveidecreases too rap? idly. The solution to this .difiiculty.wouldqapr' pear to be theprovision .ofa high. Q? circuit; But a circuithaving a sufficientlyhigh .Qfifon good calibrating purposes isdifiicult-to. obtain in actual practice.

One of the objects of this invention, therefore; is to provide a methodand-:meanato produce" in response to an electrical. impulsea givenwave-- train and/or a series. of pulse markers-ofrsubestantiallyconstant amplitude.

Another object of this invention: is 1 to provide a method andmeans forvarying the-.biaspofavacuum tube so asto efiect a -.desiredtvariation..in the gain thereof .over a given. interval of timer;

Themethod of this invention is concernedprimarily with the problemofcompensating for-the decay of a damped wave train. such .as may beproduced by shock :exciting an L--C circuitby means of an impulse suchas transmitted .for obstacle detection purposes 1 .This t. I. accomplishbygapplyingithe .dampediwave energy to :arcircuitit. oftazvacuumstube-and varying. gradually thebias otithetube :so as .to.efi'ect: a. gradualincreaseain? stanta amplitude whichever mayberequired.

For:amatter-understanding of-the methcd refi erence: mayvbe hadto. thefollowing detailed :de-

scription of several; forms of apparatus. by: which theameth'od imay bepracticed; the detailed def scriptionrto .be; read. in connection with"the ac companyingdrawings; in which-,.

Fig. 1 isreazzschematic; illustration; oica radio detectionvsystem:incorporating. apparatus made in accordance with this invention;

Fig; ,2 .iis. a r graphical. illustration of the constant:amplitudeawave train produced: and'howthe waveatrainismodifiedtoproducepulse mark-': ers; ands;

Figszfi :andi4 are schematic illustrations :of::two additional formsof.apparatus in accordance with.

this'. invention;

RieferringstogFi'g: 1 of: the drawings, a: radio.- detectinggsystema is.schematically shownincorporatingnone; of the embodiments .of this:inven'-; titl ng:v Thesystemrincludes a known typevofr transmitter lUtandxan; antenna 1 2 ;-for transmise.

sionaof 'recurringiimpulses; A receiver-- M-and: antenna I 5 ;together:with; :an oscillograph. I 6 are provided?" to receive" and: indicateecho pulsescaused: :by' "obstacles: such" as, aircraft or shipseinresponsestmthetransmitted impulses. Connecte:

ing the transmitter 1 to the receiver is the 91.18113] blocking circuit.ll; arrangedi 'toz block the re-- ceiver during; the transmission ofimpulses. The

sweepmircuit ofxthelosci-llographa I6 is controlled. byfrthesrimpulserenergy of the transmitter Hi through a: connection 58 to a sweepgenerator F92. The'interval. of time "represented. bythe -lo-.-cationrofvan': echoip'ulseon the screenof the 0s:

cill'ograph with respect to a: reference point such. asthe deft-handendmf. thetrace-line is used. to

determine-thevtime interval between the transmission. ofan impulse andan echo thereof.

This...interval.is used to determine the distance toltheiobstaclecausing the echo.

nlcalibi'atedflscal.or series of pulse markersv 3 for the screen of theoscillograph whereby the distance represented by the location of theecho pulse can be readily determined is provided. In accordance with myinvention, the generation of the pulse markers is controlled by energyof the transmitted impulse. This energy is applied over a connection 20to the grid 2| of a vacuum tube 22 which has a cathode 23 self-biased bya resistance-capacitance circuit 25 and a grid 2! connected by a gridleak 26 to the ground connection of the circuit 25. The plate 28 of thetube 22 is connected to a tuned inductancecapacitance circuit 30. Whenan impulse 32 is applied to the grid 2|, the wave front thereof isadapted to shock excite the tuned circuit 33 and thereby produce adamped wave train 33. The energy of the wave train 33 is applied over aconnection 34 to a time constant circuit includand this wave is passedthrough a difierentiating circuit 64 to produce alternately positive andnegative narrow shaped pulses 65 and 66. This pulse energy is passedthrough a class C" amplifier to produce uni-directional pulses 67, theamplifie-r being biased to cut on at the threshold line 56.

These pulses 61 are of substantially equal amplitude for the desiredlength of the trace line so that when applied to the oscillograph l6they divide the length of the trace line into equal segments which canbe easily counted to determine the location of an echo pulse appearingalong the trace line. The sweep generator 19 is preferably adjusted tobuild up to a given sweep potential and then return to zero'for eachimpulse 32 applied thereto. Such a sweep potential is indicated at ,f(Fig. 2). In this way the pulse markers 61. occurringduring the sweepportion 68 appear on the oscillograph while those pulses which occurduring the inactive portion 69 of the sweep cycle do not appear or ii.they do they In order to compensate for the decay of the" oscillationsof the damped wave train 33, a second grid electrode 42 is connected toa time constant circuit 44 which includes a condenser 45 and aresistance 46 one end of which is connected to ground as shown inFig. 1. The circuit 44 is connected to the connection 20 from thetransmitter I0. Energy of the pulse 32 is simultaneously applied to thecircuit 44 when it is applied to the grid 26 and this energy on passingthrough the time constant circuit 44 assumes .a shape substantially asshown at 48. In other words, the pulse energy 32 charges the condenser45 negatively due to the grid current flowing in the circuit 44 therebyresulting in a pulse of less amplitude than the pulse 32. The dischargeof the condenser through the resistance 46 produces an extended trailingedge for the pulse 48. This trailing edge follows an exponential curvesimilar to the decay of the wave 33.

The energy of the pulse 48 is applied to the grid 42 thereby producing asharp initial. drop 5| from the maximum gain 50 .of the tube 40 (seecharacteristic curve adjacent plate circuit 54).

'Due to the value of the resistance 46 the gain of the tube graduallyincreases back to maximum value along an exponential curve 52. Thisincrease in gain is so chosen by the values of the resistance 46 and thecondenser 45 that the decay of the wave train 33 as it is appliedthrough the time constant of the condenser 35 and resistance 36 to thetube 49 is compensated for thereby giving an output wave 53 in the plateor anode circuit 54, the oscillations of which are of substantiallyconstant amplitude for an interval of time during which the gain 52increases back to maximum. After the gain has returned to maximum value,the output wave 53 is damped oft rapidly as indicated at 55 (Fig. 2).

This resulting plate output wave 53 and its relation with respect torecurring impulses 32 are shown in parts a and b of Fig. 2. Theoscillations of this wave may be applied to an oscillograph forcalibration purposes or the wave can be passed through additional meansby which narrow marker pulses are generated. As indicated in Fig. 1 andparts I), c, d, and e of Fig. 2, the wave 53 is first clipped by passingit through a clipper 63 such as a properly biased tube whereby theoscillations of the wave are clipped as indicated by the lines BI and62. This results in a wave of substantially rectangular pulses 63 willunderlie the initial pulse occurring at the initiation of the nextcycle.

In Fig. 3 of the drawing, I have shown a modified form of the apparatusshown in Fig. 1 by which I produce substantially the same results. Iemploy here the same tube 22 and tuned circuit 30. The grid 2| hasconnected thereto the grid leak 26 and the cathode 23 is self-biased bythe circuit 25. The plate circuit 10 is connected to a time constantcircuit including a condenser H and a resistance 12 which are connectedto the grid 4| of the tube 40 similarly as in Fig. 1. The means forcompensating for the decay of the wave train 33 (Figs. 1 and 4) producedby shock excitation of the circuit 30 include a circuit 15 connectedthrough a condenser I6 to the plate circuit 10. 'This circuit 15contains a knowntype I of rectifier 18 across which is connected aresistance l9 and the output thereof is connected by a line to thesecond grid 42 of the tube 40. The cathode 43 of the tube 40 isself-biased by a resistance-condenser circuit 82 so that it will notdraw current until the grid potentials are positive. The rectifiedcurrent as indicated at 84 comprises negative direct current whichcommences at a high negative value corresponding to the amplitude of theinitial oscillation of the wave train 33 and decreases exponentially tozero value. This negative direct current is applied to the grid 42 andthereby decreases gradually the negative bias of the tube. This decreaseof the negative bias alters the gain of tube so as to substantiallyoifset the decay of the wave train 33 until the direct current returnsto zero value. The output of the tube 40 will be of the general waveshape shown in part b of Fig. 2.

In Fig. 4 another embodiment is disclosed wherein the tube 22, thecircuit 33 disclosed in Figs. 1 and 3 are employed, the plate circuit 93of which is connected through a time constant circuit including acondenser 9| and a resistance 92 applied to the grid 93 of a triode 94.The damped wave train 33 charges the condenser 9| negatively asindicated at 95 by the first positive peak thereof. The followingoscillations of the wave train 33 provide successively decreasing pulsecharges for the condenser 9!, and the smoothing out function of the highresistance 92 provides a gradually decreasing bias as indicated by thecurve 96 thereby giving an exponential variation. to the gain of thetube 94.

If the amplitude of the pulse 32 is large so that the negative peaks candrive the tube 94 eg s-3904 to platepurrent cutoff, this will effect aclipping action", insuring constant amplitude for 'a series ofpulsessuch asshown forythe'interval frat-9T. These markers may 'be applieddirectly; to' the oscillograph for calibration purposes or they 'canbepass'edthrough' a' known-pulseshaper to'narrow, them beforeapplication toan oscillograph, or they may be-applied to-a system ofclipping, differentiating and-thresholdclipping ashereinbefore describedin connection with Fig. 1.

Although I have described the system with my inventionilinconnectionwith an obstacle detection system, it' is clean'that theprinciples "set" forth are not solimited'in scope. 'Themeth'od andsystem is applicable wherever it is' desired to produce a substantiallyconstant amplitude wave train or a series of constant amplitude pulsesof limited duration in response to a single applied pulse.

While I have described above the principles of my invention inconnection with specific apparatus, and particular modificationsthereof, it is to be clearly understood that this description is madeonly by way of example and not as a limitation on the scope of myinvention as set forth in the objects of my invention and theaccompanying :claims.

What I claim is:

1. A method of producing a short wave train having a series ofoscillations of substantially constant amplitude comprising generating adamped wave train having a decay characteristic which determines theduration thereof, and compensating for the decay of the damped wavetrain for a plurality of the oscillations thereof by adding to thedamped wave train a wave of energy increasing in amplitude at a ratesubstantially proportional to the decay of said damped wave.

2. A method of producing in the output of a tube circuit a short wavetrain having a series of oscillations of substantially constantamplitude comprising amplifying a damped wave train at a ratesubstantially proportionate to the decay thereof.

3. A method of producing calibrated markers of substantially constantamplitude for the screen of an oscillograph of a radio detection systemadapted to transmit impulses and receive echoes thereof, which methodcomprises initiating generation of a damped Wave train having a givendecay characteristic which determines the duration thereof insynchronism with the transmission of an impulse, compensating for thedecay of the damped wave train for a plurality of oscillations thereof,and deriving a series of unidirectional pulse markers therefrom.

4. A method of producing uni-directional sharply pointed pulses ofsubstantially constant amplitude comprising generating a damped wavetrain having a given decay characteristic which determines the durationthereof, compensating for the decay of the damped wave train for aplurality of oscillations thereof, and deriving therefrom a series ofuni-directional pulses.

5. A system for producing a short wave train having a series ofoscillations of substantially constant amplitude comprising means togenerate a damped wave train having a given decay characteristic whichdetermines the duration thereof, means to produce a wave of energyincreasing in amplitude at a rate substantially proportional to the rateof decay of said damped wave, and means to apply said energy wave tosaid damped wave train to compensate for the decay of thedamped wavetrain for. a plurality.

of the oscillations thereof.

6." A system for producing a wave trainhaving a series of-"oscillationsof substantially constant amplitude comprising'a tube including, gridandof the dalmped wave train, thereby; producingia,

plurality of energy oscillations. of substantially constant amplitude inthe anode electrode of the tube.-

'7: The,systemdefinedinsclaim 6 whereinthe means ito efi'ectasgradualincrease in the'gain of the tube comprises a grid circuit having acondenser and a resistanceof values selected to provide a time constantsuch that the gain in the tube is increased in accordance with the decayin the osctllations of the damped wave train.

8. The system defined in claim 6 wherein the means to effect a gradualincrease in the gain of the tube comprises means to rectify a part ofthe energy of the damped wave train and means to apply the rectifiedcurrent to a grid electrode of the tube.

9. A system for producing a short wave train having a series ofoscillations of substantially constant amplitude comprising a tubeincluding grid and anode electrodes, a tuned circuit, means to applydiscrete electrical impulse to said circuit to initiate oscillations fora short period therein, means to apply energy of the oscillations to agrid electrode of the tube, and means to effect a gradual increase inthe gain of the tube to offset the decay of the oscillations produced insaid tuned circuit, thereby producing a plurality of energy oscillationsof substantially constant amplitude in the anode circuit of the tube.

10. The system defined in claim 9 wherein the means to effect a gradualincrease in the gain of the tube comprises means to reshape energy ofthe electrical impulse in accordance to an exponential time constant andmeans to apply the reshaped impulse energy to a grid electrod of thetube.

11. A system for producing calibrated pulse markers of substantiallyconstant amplitude for the screen of an oscillograph of a radiodetection system. adapted to transmit electrical impulses and receiveechoes thereof, comprising means responsive to said electrical impulsesto generate for each impulse a damped wave train, means to compensatethe decay of the damped wave for a plurality of the oscillationsthereof, means to clip the resulting oscillations to produce a wave ofsubstantially rectangular pulses, means to differentiate the wave thusproduced to form alternately positive and negative sharply pointedpulses, and means to segregate therefrom the pulses disposed in onedirection.

12. A system for producing uni-directional sharply pointed pulses ofsubstantially constant amplitude comprising a damped wave source, meansto compensate the decay of the damped wave for a plurality of theoscillations thereof, means to clip the resulting oscillations toproduce a wave of substantially rectangular pulses, means todifferentiate the wave thus produced to form alternately positive andnegative sharply pointed pulses, and means to segregate therefrom thepulses disposed in one direction.

13. A method of producing a short wave train having a series ofoscillations of substantially 7 constant amplitude comprising producinga. wave having a, decay characteristic which determines the durationthereof, and compensating the decrease of energy of said wave at a. ratesubstantially proportionate to the progressive decay The followingreferences are of record in the 10 file of this patent:

UNITED STATES PATENTS Name Date Fitch July 1, 1947 Preisman Apr. 29,1947 Number 8 Number Name Date 2,422,204 Meacham June 17, 1947 2,422,205Meacham June 17, 1947 2,103,090 Plebanski Dec. 21, 1937 2,138,138Bruckner Nov. 29, 1938 1,908,249 Hund May 9, 1933 2,264,369 Golicke Dec.2, 1941 2,167,492 Sprouls July 25, 1939 2,009,459 Turner, Jr July 30,1935 OTHER REFERENCES Proceedings of the I. R. E., vol. 28, No. 9, Sept.1940, pp. 406-409, The Generation for Television of HorizontalSynchronizing Pluses, Etc." by J. S.

15 Sherman.

